Rogers Cadenhead points us to a Real Estate namespace for RSS 2.0. About a year ago, I was looking for a real estate XML to work with on one project. I wrote down a couple requirements and was unable to find anything that met these very trivial requirements. This real estate namespace doesn't meet those simple requirements either. For instance, when I was looking for a house 2 years ago, I wanted to filter out all properties that had swimming pools. I couldn't do that and this namespace doesn't allow for that either. The problem is that the authors of this XML tried to create an extension for RSS 2.0 and not a real estate vocabulary for XML. This is a recipe for incompleteness. A better approach is to take an existing real estate XML and describe how to use it with RSS 2.0.
http://www.propsmart.com/datafeed
There is a Real Estate Transaction XML called RETS. A year ago, I considered basing my project on that XML, but it was complex to the point where it was unusable. There seems to be a large gap between incomplete and usable that begs to be filled.
It's actually a tribute to RSS that despite its inconsistencies, it has remained rather simple.
--Sterling Camden